Method and apparatus for processing data units in wireless communication system

ABSTRACT

The present invention relates to a method for processing data units by a Packet Data Convergence Protocol (PDCP) entity of a user equipment (UE) in a wireless communication system. In particular, the method includes the steps of: receiving a first data unit having a specific count value from a lower layer; and discarding the first data unit, when there is a second data unit having the specific count value which was received before the first data unit and for which an integrity verification was successful.

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2019/010429 filed Aug. 16, 2019,which claims the benefit of Korean Application No. 10-2018-0114645 filedSep. 27, 2018, the contents of which are all hereby incorporated byreference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system.Especially, the present invention relates to processing data units by aPacket Data Convergence Protocol (PDCP) entity of a user equipment in awireless communication system.

BACKGROUND ART

Introduction of new radio communication technologies has led toincreases in the number of user equipments (UEs) to which a base station(BS) provides services in a prescribed resource region, and has also ledto increases in the amount of data and control information that the BStransmits to the UEs. Due to typically limited resources available tothe BS for communication with the UE(s), new techniques are needed bywhich the BS utilizes the limited radio resources to efficientlyreceive/transmit uplink/downlink data and/or uplink/downlink controlinformation. In particular, overcoming delay or latency has become animportant challenge in applications whose performance critically dependson delay/latency.

DISCLOSURE OF INVENTION

Technical Problem

Accordingly, an object of the present invention is to provide a methodof processing data units by a Packet Data Convergence Protocol (PDCP)entity of a user equipment in a wireless communication system andapparatus therefore.

Solution to Problem

The object of the present invention can be achieved by the method ofprocessing data units by a Packet Data Convergence Protocol (PDCP)entity of a user equipment (UE) in a wireless communication system, themethod comprising: receiving a first data unit having a specific countvalue from a lower layer; and discarding the first data unit, when thereis a second data unit having the specific count value which was receivedbefore the first data unit and for which an integrity verification wassuccessful.

Further, it is suggested a user equipment (UE) in a wirelesscommunication system comprising a memory; and at least one processorcoupled to the memory. More specifically, the at least one processorcontrols a Packet Data Convergence Protocol (PDCP) entity of the UE toreceive a first data unit having a specific count value from a lowerlayer; and discard the first data unit, when there is a second data unithaving the specific count value which was received before the first dataunit and for which an integrity verification was successful.

Preferably, the UE (i.e., the PDCP entity of the UE) should perform anintegrity verification for the first data unit; and store the first dataunit in a buffer, when integrity verification for the first data unit issuccessful and when the integrity verification for the second data unitwas not successful. More preferably, the UE (i.e., the PDCP entity ofthe UE) should discard the first data unit when integrity verificationfor the first data unit is not successful.

Preferably, the UE (i.e., the PDCP entity of the UE) should determinewhether the first data unit is to be discarded or not based on a resultof the integrity verification for the first data unit, when there is asecond data unit having the specific count value which was receivedbefore the first data unit and for which an integrity verification isnot successful.

Preferably, the at least one processor is further configured toimplement at least one advanced driver assistance system (ADAS) functionbased on signals that control the UE.

Advantageous Effects of Invention

According to the aforementioned embodiments of the present invention,the PDCP entity of the UE can process data units efficiently.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an example of a network structure of anevolved universal mobile telecommunication system (E-UMTS) as anexemplary radio communication system;

FIG. 2 is a block diagram illustrating an example of an evolveduniversal terrestrial radio access network (E-UTRAN);

FIG. 3 is a block diagram depicting an example of an architecture of atypical E-UTRAN and a typical EPC;

FIG. 4 is a diagram showing an example of a control plane and a userplane of a radio interface protocol between a UE and an E-UTRAN based ona 3GPP radio access network standard;

FIG. 5 is a diagram showing an example of a physical channel structureused in an E-UMTS system;

FIG. 6 illustrates an example of protocol stacks of a next generationwireless communication system;

FIG. 7 illustrates an example of a data flow example at a transmittingdevice in the NR system;

FIG. 8 illustrates an example of a slot structure available in a newradio access technology (NR);

FIG. 9 shows a flow chart of the present invention;

FIG. 10 shows an example according to an embodiment of the presentinvention; and

FIG. 11 is a block diagram illustrating an example of elements of atransmitting device 100 and a receiving device 200 according to someimplementations of the present disclosure.

BEST MODE FOR CARRYING OUT THE INVENTION

The technical objects that can be achieved through the presentdisclosure are not limited to what has been particularly describedhereinabove and other technical objects not described herein will bemore clearly understood by persons skilled in the art from the followingdetailed description.

FIG. 1 is a diagram illustrating an example of a network structure of anE-UMTS as an exemplary radio communication system. An Evolved UniversalMobile Telecommunications System (E-UMTS) is an advanced version of aUniversal Mobile Telecommunications System (UMTS) and basicstandardization thereof is currently underway in the 3GPP. E-UMTS may begenerally referred to as a Long Term Evolution (LTE) system. For detailsof the technical specifications of the UMTS and E-UMTS, reference can bemade to Release 7 and Release 8 of “3rd Generation Partnership Project;Technical Specification Group Radio Access Network”.

Referring to FIG. 1 , the E-UMTS includes a User Equipment (UE), eNodeBs (eNBs), and an Access Gateway (AG) which is located at an end of thenetwork (E-UTRAN) and connected to an external network. The eNBs maysimultaneously transmit multiple data streams for a broadcast service, amulticast service, and/or a unicast service.

One or more cells may exist per eNB. The cell is set to operate in oneof bandwidths such as 1.25, 2.5, 5, 10, 15, and 20 MHz and provides adownlink (DL) or uplink (UL) transmission service to a plurality of UEsin the bandwidth. Different cells may be set to provide differentbandwidths. The eNB controls data transmission or reception to and froma plurality of UEs. The eNB transmits DL scheduling information about DLdata to a corresponding UE so as to inform the UE of a time/frequencydomain in which the DL data is supposed to be transmitted, coding, adata size, and hybrid automatic repeat and request (HARQ)-relatedinformation. In addition, the eNB transmits UL scheduling informationabout UL data to a corresponding UE so as to inform the UE of atime/frequency domain which may be used by the UE, coding, a data size,and HARQ-related information. An interface for transmitting user trafficor control traffic may be used between eNBs. A core network (CN) mayinclude the AG and a network node or the like for user registration ofUEs. The AG manages the mobility of a UE on a tracking area (TA) basis.One TA includes a plurality of cells.

Although wireless communication technology has been developed to LTEbased on wideband code division multiple access (WCDMA), the demands andexpectations of users and service providers are on the rise. Inaddition, considering other radio access technologies under development,new technological evolution is required to secure high competitivenessin the future. Decrease in cost per bit, increase in serviceavailability, flexible use of frequency bands, a simplified structure,an open interface, appropriate power consumption of UEs, and the likeare required.

As more and more communication devices demand larger communicationcapacity, there is a need for improved mobile broadband communicationcompared to existing RAT. Also, massive machine type communication(MTC), which provides various services by connecting many devices andobjects, is one of the major issues to be considered in the nextgeneration communication. In addition, a communication system designconsidering a service/UE sensitive to reliability and latency is beingdiscussed. The introduction of next-generation RAT, which takes intoaccount such advanced mobile broadband communication, massive MTC(mMCT), and ultra-reliable and low latency communication (URLLC), isbeing discussed.

Reference will now be made in detail to the exemplary implementations ofthe present disclosure, examples of which are illustrated in theaccompanying drawings. The detailed description, which will be givenbelow with reference to the accompanying drawings, is intended toexplain exemplary implementations of the present disclosure, rather thanto show the only implementations that can be implemented according tothe disclosure. The following detailed description includes specificdetails in order to provide a thorough understanding of the presentdisclosure. However, it will be apparent to those skilled in the artthat the present disclosure may be practiced without such specificdetails.

The following techniques, apparatuses, and systems may be applied to avariety of wireless multiple access systems. Examples of the multipleaccess systems include a code division multiple access (CDMA) system, afrequency division multiple access (FDMA) system, a time divisionmultiple access (TDMA) system, an orthogonal frequency division multipleaccess (OFDMA) system, a single carrier frequency division multipleaccess (SC-FDMA) system, and a multicarrier frequency division multipleaccess (MC-FDMA) system. CDMA may be embodied through radio technologysuch as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe embodied through radio technology such as global system for mobilecommunications (GSM), general packet radio service (GPRS), or enhanceddata rates for GSM evolution (EDGE). OFDMA may be embodied through radiotechnology such as institute of electrical and electronics engineers(IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or evolved UTRA(E-UTRA). UTRA is a part of a universal mobile telecommunications system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employsOFDMA in DL and SC-FDMA in UL. LTE-advanced (LTE-A) is an evolvedversion of 3GPP LTE. For convenience of description, implementations ofthe present disclosure are described in regards to a 3GPP based wirelesscommunication system. However, the technical features of the presentdisclosure are not limited thereto. For example, although the followingdetailed description is given based on a mobile communication systemcorresponding to a 3GPP based system, aspects of the present disclosurethat are not limited to 3GPP based system are applicable to other mobilecommunication systems.

For example, the present disclosure is applicable to contention basedcommunication such as Wi-Fi as well as non-contention basedcommunication as in the 3GPP based system in which a BS allocates aDL/UL time/frequency resource to a UE and the UE receives a DL signaland transmits a UL signal according to resource allocation of the BS. Ina non-contention based communication scheme, an access point (AP) or acontrol node for controlling the AP allocates a resource forcommunication between the UE and the AP, whereas, in a contention basedcommunication scheme, a communication resource is occupied throughcontention between UEs which desire to access the AP. The contentionbased communication scheme will now be described in brief. One type ofthe contention based communication scheme is carrier sense multipleaccess (CSMA). CSMA refers to a probabilistic media access control (MAC)protocol for confirming, before a node or a communication devicetransmits traffic on a shared transmission medium (also called a sharedchannel) such as a frequency band, that there is no other traffic on thesame shared transmission medium. In CSMA, a transmitting devicedetermines whether another transmission is being performed beforeattempting to transmit traffic to a receiving device. In other words,the transmitting device attempts to detect presence of a carrier fromanother transmitting device before attempting to perform transmission.Upon sensing the carrier, the transmitting device waits for anothertransmission device which is performing transmission to finishtransmission, before performing transmission thereof. Consequently, CSMAcan be a communication scheme based on the principle of “sense beforetransmit” or “listen before talk”. A scheme for avoiding collisionbetween transmitting devices in the contention based communicationsystem using CSMA includes carrier sense multiple access with collisiondetection (CSMA/CD) and/or carrier sense multiple access with collisionavoidance (CSMA/CA). CSMA/CD is a collision detection scheme in a wiredlocal area network (LAN) environment. In CSMA/CD, a personal computer(PC) or a server which desires to perform communication in an Ethernetenvironment first confirms whether communication occurs on a networkand, if another device carries data on the network, the PC or the serverwaits and then transmits data. That is, when two or more users (e.g.PCs, UEs, etc.) simultaneously transmit data, collision occurs betweensimultaneous transmission and CSMA/CD is a scheme for flexiblytransmitting data by monitoring collision. A transmitting device usingCSMA/CD adjusts data transmission thereof by sensing data transmissionperformed by another device using a specific rule. CSMA/CA is a MACprotocol specified in IEEE 802.11 standards. A wireless LAN (WLAN)system conforming to IEEE 802.11 standards does not use CSMA/CD whichhas been used in IEEE 802.3 standards and uses CA, i.e. a collisionavoidance scheme. Transmission devices always sense carrier of a networkand, if the network is empty, the transmission devices wait fordetermined time according to locations thereof registered in a list andthen transmit data. Various methods are used to determine priority ofthe transmission devices in the list and to re-configure priority. In asystem according to some versions of IEEE 802.11 standards, collisionmay occur and, in this case, a collision sensing procedure is performed.A transmission device using CSMA/CA avoids collision between datatransmission thereof and data transmission of another transmissiondevice using a specific rule.

In the present disclosure, a user equipment (UE) may be a fixed ormobile device.

Examples of the UE include various devices that transmit and receiveuser data and/or various kinds of control information to and from a basestation (BS). The UE may be referred to as a terminal equipment (TE), amobile station (MS), a mobile terminal (MT), a user terminal (UT), asubscriber station (SS), a wireless device, a personal digital assistant(PDA), a wireless modem, a handheld device, etc. In addition, in thepresent disclosure, a BS generally refers to a fixed station thatperforms communication with a UE and/or another BS, and exchangesvarious kinds of data and control information with the UE and anotherBS. The BS may be referred to as an advanced base station (ABS), anode-B (NB), an evolved node-B (eNB), a base transceiver system (BTS),an access point (AP), a processing server (PS), etc. Especially, a BS ofthe UMTS is referred to as a NB, a BS of the EPC/LTE is referred to asan eNB, and a BS of the new radio (NR) system is referred to as a gNB.

In the present disclosure, a node refers to a fixed point capable oftransmitting/receiving a radio signal through communication with a UE.Various types of BSs may be used as nodes irrespective of the termsthereof. For example, a BS, a node B (NB), an e-node B (eNB), apico-cell eNB (PeNB), a home eNB (HeNB), a relay, a repeater, etc. maybe a node. In addition, the node may not be a BS. For example, the nodemay be a radio remote head (RRH) or a radio remote unit (RRU). The RRHor RRU generally has a lower power level than a power level of a BS.Since the RRH or RRU (hereinafter, RRH/RRU) is generally connected tothe BS through a dedicated line such as an optical cable, cooperativecommunication between RRH/RRU and the BS can be smoothly performed incomparison with cooperative communication between BSs connected by aradio line. At least one antenna is installed per node. The antenna mayinclude a physical antenna or an antenna port or a virtual antenna.

In the present disclosure, a cell refers to a prescribed geographicalarea to which one or more nodes provide a communication service.Accordingly, in the present disclosure, communicating with a specificcell may include communicating with a BS or a node which provides acommunication service to the specific cell. In addition, a DL/UL signalof a specific cell refers to a DL/UL signal from/to a BS or a node whichprovides a communication service to the specific cell. A node providingUL/DL communication services to a UE is called a serving node and a cellto which UL/DL communication services are provided by the serving nodeis especially called a serving cell.

In some scenarios, a 3GPP based system implements a cell to manage radioresources and a cell associated with the radio resources isdistinguished from a cell of a geographic region.

A “cell” of a geographic region may be understood as coverage withinwhich a node can provide service using a carrier and a “cell” of a radioresource is associated with bandwidth (BW) which is a frequency rangeconfigured by the carrier. Since DL coverage, which is a range withinwhich the node is capable of transmitting a valid signal, and ULcoverage, which is a range within which the node is capable of receivingthe valid signal from the UE, depends upon a carrier carrying thesignal, the coverage of the node may be associated with coverage of the“cell” of a radio resource used by the node. Accordingly, the term“cell” may be used to indicate service coverage of the node sometimes, aradio resource at other times, or a range that a signal using a radioresource can reach with valid strength at other times.

In some scenarios, the recent 3GPP based wireless communication standardimplements a cell to manage radio resources. The “cell” associated withthe radio resources utilizes a combination of downlink resources anduplink resources, for example, a combination of DL component carrier(CC) and UL CC. The cell may be configured by downlink resources only,or may be configured by downlink resources and uplink resources. Ifcarrier aggregation is supported, linkage between a carrier frequency ofthe downlink resources (or DL CC) and a carrier frequency of the uplinkresources (or UL CC) may be indicated by system information. Forexample, combination of the DL resources and the UL resources may beindicated by linkage of system information block type 2 (SIB2). In thiscase, the carrier frequency may be a center frequency of each cell orCC. A cell operating on a primary frequency may be referred to as aprimary cell (Pcell) or PCC, and a cell operating on a secondaryfrequency may be referred to as a secondary cell (Scell) or SCC. Thecarrier corresponding to the Pcell on downlink will be referred to as adownlink primary CC (DL PCC), and the carrier corresponding to the Pcellon uplink will be referred to as an uplink primary CC (UL PCC). A Scellrefers to a cell that may be configured after completion of radioresource control (RRC) connection establishment and used to provideadditional radio resources. The Scell may form a set of serving cellsfor the UE together with the Pcell in accordance with capabilities ofthe UE. The carrier corresponding to the Scell on the downlink will bereferred to as downlink secondary CC (DL SCC), and the carriercorresponding to the Scell on the uplink will be referred to as uplinksecondary CC (UL SCC). Although the UE is in RRC-CONNECTED state, if itis not configured by carrier aggregation or does not support carrieraggregation, a single serving cell configured by the Pcell only exists.

In the present disclosure, “PDCCH” refers to a PDCCH, an EPDCCH (insubframes when configured), a MTC PDCCH (MPDCCH), for an RN with R-PDCCHconfigured and not suspended, to the R-PDCCH or, for NB-IoT to thenarrowband PDCCH (NPDCCH).

In the present disclosure, monitoring a channel refers to attempting todecode the channel. For example, monitoring a PDCCH refers to attemptingto decode PDCCH(s) (or PDCCH candidates).

For terms and technologies which are not specifically described amongthe terms of and technologies employed in this specification, 3GPPLTE/LTE-A standard documents, for example, 3GPP TS 36.211, 3GPP TS36.212, 3GPP TS 36.213, 3GPP TS 36.300, 3GPP TS 36.321, 3GPP TS 36.322,3GPP TS 36.323 and 3GPP TS 36.331, and 3GPP NR standard documents, forexample, 3GPP TS 38.211, 3GPP TS 38.213, 3GPP TS 38.214, 3GPP TS 38.300,3GPP TS 38.321, 3GPP TS 38.322, 3GPP TS 38.323 and 3GPP TS 38.331 may bereferenced.

FIG. 2 is a block diagram illustrating an example of an evolveduniversal terrestrial radio access network (E-UTRAN). The E-UMTS may bealso referred to as an LTE system. The communication network is widelydeployed to provide a variety of communication services such as voice(VoIP) through IMS and packet data.

As illustrated in FIG. 2 , the E-UMTS network includes an evolved UMTSterrestrial radio access network (E-UTRAN), an Evolved Packet Core (EPC)and one or more user equipment. The E-UTRAN may include one or moreevolved NodeB (eNodeB) 20, and a plurality of user equipments (UE) 10may be located in one cell. One or more E-UTRAN mobility managemententity (MME)/system architecture evolution (SAE) gateways 30 may bepositioned at the end of the network and connected to an externalnetwork.

As used herein, “downlink” refers to communication from BS 20 to UE 10,and “uplink” refers to communication from the UE to a BS.

FIG. 3 is a block diagram depicting an example of an architecture of atypical E-TRAN and a typical EPC.

As illustrated in FIG. 3 , an eNB 20 provides end points of a user planeand a control plane to the UE 10. MME/SAE gateway 30 provides an endpoint of a session and mobility management function for UE 10. The eNBand MME/SAE gateway may be connected via an S1 interface.

The eNB 20 is generally a fixed station that communicates with a UE 10,and may also be referred to as a base station (BS) or an access point.One eNB 20 may be deployed per cell. An interface for transmitting usertraffic or control traffic may be used between eNBs 20.

The MME provides various functions including NAS signaling to eNBs 20,NAS signaling security, access stratum (AS) Security control, Inter CNnode signaling for mobility between 3GPP access networks, Idle mode UEReachability (including control and execution of paging retransmission),Tracking Area list management (for UE in idle and active mode), PDN GWand Serving GW selection, MME selection for handovers with MME change,SGSN selection for handovers to 2G or 3G 3GPP access networks, roaming,authentication, bearer management functions including dedicated bearerestablishment, support for PWS (which includes ETWS and CMAS) messagetransmission. The SAE gateway host provides assorted functions includingPer-user based packet filtering (by e.g. deep packet inspection), LawfulInterception, UE IP address allocation, Transport level packet markingin the downlink, UL and DL service level charging, gating and rateenforcement, DL rate enforcement based on APN-AMBR. For clarity MME/SAEgateway 30 will be referred to herein simply as a “gateway,” but it isunderstood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNB 20 and gateway 30 viathe S1 interface. The eNBs 20 may be connected to each other via an X2interface and neighboring eNBs may have a meshed network structure thathas the X2 interface.

As illustrated, eNB 20 may perform functions of selection for gateway30, routing toward the gateway during a Radio Resource Control (RRC)activation, scheduling and transmitting of paging messages, schedulingand transmitting of Broadcast Channel (BCCH) information, dynamicallocation of resources to UEs 10 in both uplink and downlink,configuration and provisioning of eNB measurements, radio bearercontrol, radio admission control (RAC), and connection mobility controlin LTE_ACTIVE state. In the EPC, and as noted above, gateway 30 mayperform functions of paging origination, LTE-IDLE state management,ciphering of the user plane, System Architecture Evolution (SAE) bearercontrol, and ciphering and integrity protection of Non-Access Stratum(NAS) signaling.

The EPC includes a mobility management entity (MME), a serving-gateway(S-GW), and a packet data network-gateway (PDN-GW). The MME hasinformation about connections and capabilities of UEs, mainly for use inmanaging the mobility of the UEs. The S-GW is a gateway having theE-UTRAN as an end point, and the PDN-GW is a gateway having a packetdata network (PDN) as an end point.

FIG. 4 is a diagram showing an example of a control plane and a userplane of a radio interface protocol between a UE and an E-UTRAN based ona 3GPP radio access network standard. The control plane refers to a pathused for transmitting control messages used for managing a call betweenthe UE and the E-UTRAN. The user plane refers to a path used fortransmitting data generated in an application layer, e.g., voice data orInternet packet data.

Layer 1 (i.e. L1) of the 3GPP LTE/LTE-A system is corresponding to aphysical layer. A physical (PHY) layer of a first layer (Layer 1 or L1)provides an information transfer service to a higher layer using aphysical channel. The PHY layer is connected to a medium access control(MAC) layer located on the higher layer via a transport channel. Data istransported between the MAC layer and the PHY layer via the transportchannel. Data is transported between a physical layer of a transmittingside and a physical layer of a receiving side via physical channels. Thephysical channels use time and frequency as radio resources. In detail,the physical channel is modulated using an orthogonal frequency divisionmultiple access (OFDMA) scheme in downlink and is modulated using asingle carrier frequency division multiple access (SC-FDMA) scheme inuplink.

Layer 2 (i.e. L2) of the 3GPP LTE/LTE-A system is split into thefollowing sublayers: Medium Access Control (MAC), Radio Link Control(RLC) and Packet Data Convergence Protocol (PDCP). The MAC layer of asecond layer (Layer 2 or L2) provides a service to a radio link control(RLC) layer of a higher layer via a logical channel. The RLC layer ofthe second layer supports reliable data transmission. A function of theRLC layer may be implemented by a functional block of the MAC layer. Apacket data convergence protocol (PDCP) layer of the second layerperforms a header compression function to reduce unnecessary controlinformation for efficient transmission of an Internet protocol (IP)packet such as an IP version 4 (IPv4) packet or an IP version 6 (IPv6)packet in a radio interface having a relatively small bandwidth.

The main services and functions of the MAC sublayer include: mappingbetween logical channels and transport channels;multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels; scheduling information reporting;error correction through HARQ; priority handling between logicalchannels of one UE; priority handling between UEs by dynamic scheduling;MBMS service identification; transport format selection; and padding.

The main services and functions of the RLC sublayer include: transfer ofupper layer protocol data units (PDUs); error correction through ARQ(only for acknowledged mode (AM) data transfer); concatenation,segmentation and reassembly of RLC service data units (SDUs) (only forunacknowledged mode (UM) and acknowledged mode (AM) data transfer);re-segmentation of RLC data PDUs (only for AM data transfer); reorderingof RLC data PDUs (only for UM and AM data transfer); duplicate detection(only for UM and AM data transfer); protocol error detection (only forAM data transfer); RLC SDU discard (only for UM and AM data transfer);and RLC reestablishment, except for a NB-IoT UE that only uses ControlPlane CIoT EPS optimizations.

The main services and functions of the PDCP sublayer for the user planeinclude: header compression and decompression (ROHC only); transfer ofuser data; in-sequence delivery of upper layer PDUs at PDCPre-establishment procedure for RLC AM; for split bearers in DC and LWAbearers (only support for RLC AM), PDCP PDU routing for transmission andPDCP PDU reordering for reception; duplicate detection of lower layerSDUs at PDCP re-establishment procedure for RLC AM; retransmission ofPDCP SDUs at handover and, for split bearers in DC and LWA bearers, ofPDCP PDUs at PDCP data-recovery procedure, for RLC AM; ciphering anddeciphering; timer-based SDU discard in uplink. The main services andfunctions of the PDCP for the control plane include: ciphering andintegrity protection; and transfer of control plane data. For split andLWA bearers, PDCP supports routing and reordering. For DRBs mapped onRLC AM and for LWA bearers, the PDCP entity uses the reordering functionwhen the PDCP entity is associated with two AM RLC entities, when thePDCP entity is configured for a LWA bearer; or when the PDCP entity isassociated with one AM RLC entity after it was, according to the mostrecent reconfiguration, associated with two AM RLC entities orconfigured for a LWA bearer without performing PDCP re-establishment.

Layer 3 (i.e. L3) of the LTE/LTE-A system includes the followingsublayers: Radio Resource Control (RRC) and Non Access Stratum (NAS). Aradio resource control (RRC) layer located at the bottom of a thirdlayer is defined only in the control plane. The RRC layer controlslogical channels, transport channels, and physical channels in relationto configuration, re-configuration, and release of radio bearers (RBs).An RB refers to a service that the second layer provides for datatransmission between the UE and the E-UTRAN. To this end, the RRC layerof the UE and the RRC layer of the E-UTRAN exchange RRC messages witheach other. The non-access stratum (NAS) layer positioned over the RRClayer performs functions such as session management and mobilitymanagement.

Radio bearers are roughly classified into (user) data radio bearers(DRBs) and signaling radio bearers (SRBs). SRBs are defined as radiobearers (RBs) that are used only for the transmission of RRC and NASmessages.

In LTE, one cell of the eNB is set to operate in one of bandwidths suchas 1.25, 2.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to a plurality of UEs in the bandwidth. Differentcells may be set to provide different bandwidths.

Downlink transport channels for transmission of data from the E-UTRAN tothe UE include a broadcast channel (BCH) for transmission of systeminformation, a paging channel (PCH) for transmission of paging messages,and a downlink shared channel (SCH) for transmission of user traffic orcontrol messages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted through the downlink SCH and mayalso be transmitted through a separate downlink multicast channel (MCH).

Uplink transport channels for transmission of data from the UE to theE-UTRAN include a random access channel (RACH) for transmission ofinitial control messages and an uplink SCH for transmission of usertraffic or control messages. Logical channels that are defined above thetransport channels and mapped to the transport channels include abroadcast control channel (BCCH), a paging control channel (PCCH), acommon control channel (CCCH), a multicast control channel (MCCH), and amulticast traffic channel (MTCH).

FIG. 5 is a diagram showing an example of a physical channel structureused in an E-UMTS system. A physical channel includes several subframeson a time axis and several subcarriers on a frequency axis. Here, onesubframe includes a plurality of symbols on the time axis. One subframeincludes a plurality of resource blocks and one resource block includesa plurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use certain subcarriers of certain symbols (e.g., a firstsymbol) of a subframe for a physical downlink control channel (PDCCH),that is, an L1/L2 control channel. The PDCCH carries schedulingassignments and other control information. In FIG. 5 , an L1/L2 controlinformation transmission area (PDCCH) and a data area (PDSCH) are shown.In one implementation, a radio frame of 10 ms is used and one radioframe includes 10 subframes. In addition, in LTE, one subframe includestwo consecutive slots. The length of one slot may be 0.5 ms. Inaddition, one subframe includes a plurality of OFDM symbols and aportion (e.g., a first symbol) of the plurality of OFDM symbols may beused for transmitting the L1/L2 control information.

A time interval in which one subframe is transmitted is defined as atransmission time interval (TTI). Time resources may be distinguished bya radio frame number (or radio frame index), a subframe number (orsubframe index), a slot number (or slot index), and the like. TTI refersto an interval during which data may be scheduled. For example, in the3GPP LTE/LTE-A system, an opportunity of transmission of an UL grant ora DL grant is present every 1 ms, and the UL/DL grant opportunity doesnot exists several times in less than 1 ms. Therefore, the TTI in thelegacy 3GPP LTE/LTE-A system is 1 ms.

A base station and a UE mostly transmit/receive data via a PDSCH, whichis a physical channel, using a downlink shared channel (DL-SCH) which isa transmission channel, except a certain control signal or certainservice data. Information indicating to which UE (one or a plurality ofUEs) PDSCH data is transmitted and how the UE receive and decode PDSCHdata is transmitted in a state of being included in the PDCCH.

For example, in one implementation, a certain PDCCH is CRC-masked with aradio network temporary identity (RNTI) “A” and information about datais transmitted using a radio resource “B” (e.g., a frequency location)and transmission format information “C” (e.g., a transmission blocksize, modulation, coding information or the like) via a certainsubframe. Then, one or more UEs located in a cell monitor the PDCCHusing its RNTI information. And, a specific UE with RNTI “A” reads thePDCCH and then receives the PDSCH indicated by B and C in the PDCCHinformation. In the present disclosure, a PDCCH addressed to an RNTIrefers to the PDCCH being cyclic redundancy check masked (CRC-masked)with the RNTI. A UE may attempt to decode a PDCCH using the certain RNTIif the UE is monitoring a PDCCH addressed to the certain RNTI.

A fully mobile and connected society is expected in the near future,which will be characterized by a tremendous amount of growth inconnectivity, traffic volume and a much broader range of usagescenarios. Some typical trends include explosive growth of data traffic,great increase of connected devices and continuous emergence of newservices. Besides the market requirements, the mobile communicationsociety itself also requires a sustainable development of theeco-system, which produces the needs to further improve systemefficiencies, such as spectrum efficiency, energy efficiency,operational efficiency, and cost efficiency. To meet the aboveever-increasing requirements from market and mobile communicationsociety, next generation access technologies are expected to emerge inthe near future.

Building upon its success of IMT-2000 (3G) and IMT-Advanced (4G), 3GPPhas been devoting its effort to IMT-2020 (5G) development sinceSeptember 2015. 5G New Radio (NR) is expected to expand and supportdiverse use case scenarios and applications that will continue beyondthe current IMT-Advanced standard, for instance, enhanced MobileBroadband (eMBB), Ultra Reliable Low Latency Communication (URLLC) andmassive Machine Type Communication (mMTC). eMBB is targeting high datarate mobile broadband services, such as seamless data access bothindoors and outdoors, and AR/VR applications; URLLC is defined forapplications that have stringent latency and reliability requirements,such as vehicular communications that can enable autonomous driving andcontrol network in industrial plants; mMTC is the basis for connectivityin IoT, which allows for infrastructure management, environmentalmonitoring, and healthcare applications.

FIG. 6 illustrates an example of protocol stacks of a next generationwireless communication system. In particular, FIG. 6(a) illustrates anexample of a radio interface user plane protocol stack between a UE anda gNB and FIG. 6(b) illustrates an example of a radio interface controlplane protocol stack between a UE and a gNB.

The control plane refers to a path through which control messages usedto manage call by a UE and a network are transported. The user planerefers to a path through which data generated in an application layer,for example, voice data or Internet packet data are transported.

Referring to FIG. 6(a), the user plane protocol stack may be dividedinto a first layer (Layer 1) (i.e., a physical layer (PHY) layer) and asecond layer (Layer 2).

Referring to FIG. 6(b), the control plane protocol stack may be dividedinto Layer 1 (i.e., a PHY layer), Layer 2, Layer 3 (e.g., a radioresource control (RRC) layer), and a non-access stratum (NAS) layer.

The overall protocol stack architecture for the NR system might besimilar to that of the LTE/LTE-A system, but some functionalities of theprotocol stacks of the LTE/LTE-A system should be modified in the NRsystem in order to resolve the weakness or drawback of LTE. RAN WG2 forNR is in charge of the radio interface architecture and protocols. Thenew functionalities of the control plane include the following:on-demand system information delivery to reduce energy consumption andmitigate interference, two-level (i.e. Radio Resource Control (RRC) andMedium Access Control (MAC)) mobility to implement seamless handover,beam based mobility management to accommodate high frequency, RRCinactive state to reduce state transition latency and improve UE batterylife. The new functionalities of the user plane aim at latency reductionby optimizing existing functionalities, such as concatenation andreordering relocation, and RLC out of order delivery. In addition, a newuser plane AS protocol layer named as Service Data Adaptation Protocol(SDAP) has been introduced to handle flow-based Quality of Service (QoS)framework in RAN, such as mapping between QoS flow and a data radiobearer, and QoS flow ID marking. Hereinafter the layer 2 according tothe current agreements for NR is briefly discussed.

The layer 2 of NR is split into the following sublayers: Medium AccessControl (MAC), Radio Link Control (RLC), Packet Data ConvergenceProtocol (PDCP) and Service Data Adaptation Protocol (SDAP). Thephysical layer offers to the MAC sublayer transport channels, the MACsublayer offers to the RLC sublayer logical channels, the RLC sublayeroffers to the PDCP sublayer RLC channels, the PDCP sublayer offers tothe SDAP sublayer radio bearers, and the SDAP sublayer offers to 5GC QoSflows. Radio bearers are categorized into two groups: data radio bearers(DRB) for user plane data and signalling radio bearers (SRB) for controlplane data.

The main services and functions of the MAC sublayer of NR include:mapping between logical channels and transport channels;multiplexing/demultiplexing of MAC SDUs belonging to one or differentlogical channels into/from transport blocks (TB) delivered to/from thephysical layer on transport channels; scheduling information reporting;error correction through HARQ (one HARQ entity per carrier in case ofcarrier aggregation); priority handling between UEs by dynamicscheduling; priority handling between logical channels of one UE bylogical channel prioritization; and padding. A single MAC entity cansupport one or multiple numerologies and/or transmission timings, andmapping restrictions in logical channel prioritisation controls whichnumerology and/or transmission timing a logical channel can use.

The RLC sublayer of NR supports three transmission modes: TransparentMode (TM); Unacknowledged Mode (UM); Acknowledged Mode (AM). The RLCconfiguration is per logical channel with no dependency on numerologiesand/or TTI durations, and ARQ can operate on any of the numerologiesand/or TTI durations the logical channel is configured with. For SRBO,paging and broadcast system information, TM mode is used. For other SRBsAM mode used. For DRBs, either UM or AM mode are used. The main servicesand functions of the RLC sublayer depend on the transmission mode andinclude: transfer of upper layer PDUs; sequence numbering independent ofthe one in PDCP (UM and AM); error correction through ARQ (AM only);segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs;Reassembly of SDU (AM and UM); duplicate detection (AM only); RLC SDUdiscard (AM and UM); RLC re-establishment; and protocol error detection(AM only). The ARQ within the RLC sublayer of NR has the followingcharacteristics: ARQ retransmits RLC PDUs or RLC PDU segments based onRLC status reports; polling for RLC status report is used when needed byRLC; and RLC receiver can also trigger RLC status report after detectinga missing RLC PDU or RLC PDU segment.

The main services and functions of the PDCP sublayer of NR for the userplane include: sequence numbering; header compression and decompression(ROHC only); transfer of user data; reordering and duplicate detection;PDCP PDU routing (in case of split bearers); retransmission of PDCPSDUs; ciphering, deciphering and integrity protection; PDCP SDU discard;PDCP re-establishment and data recovery for RLC AM; and duplication ofPDCP PDUs. The main services and functions of the PDCP sublayer of NRfor the control plane include: sequence numbering; ciphering,deciphering and integrity protection; transfer of control plane data;reordering and duplicate detection; and duplication of PDCP PDUs.

The main services and functions of SDAP include: mapping between a QoSflow and a data radio bearer; marking QoS flow ID (QFI) in both DL andUL packets. A single protocol entity of SDAP is configured for eachindividual PDU session. Compared to LTE's QoS framework, which isbearer-based, the 5G system adopts the QoS flow-based framework. The QoSflow-based framework enables flexible mapping of QoS flow to DRB bydecoupling QoS flow and the radio bearer, allowing more flexible QoScharacteristic configuration.

The main services and functions of RRC sublayer of NR include: broadcastof system information related to access stratum (AS) and non-accessstratum (NAS); paging initiated by a 5GC or an NG-RAN; establishment,maintenance, and release of RRC connection between a UE and a NG-RAN(which further includes modification and release of carrier aggregationand further includes modification and release of the DC between anE-UTRAN and an NR or in the NR; a security function including keymanagement; establishment, configuration, maintenance, and release ofSRB(s) and DRB(s); handover and context transfer; UE cell selection andre-release and control of cell selection/re-selection; a mobilityfunction including mobility between RATs; a QoS management function, UEmeasurement report, and report control; detection of radio link failureand discovery from radio link failure; and NAS message transfer to a UEfrom a NAS and NAS message transfer to the NAS from the UE.

Hereinafter, 5G communication system is briefly introduced.

Three main requirement categories for 5G include (1) a category ofenhanced mobile broadband (eMBB), (2) a category of massive machine typecommunication (mMTC), and (3) a category of ultra-reliable and lowlatency communications (URLLC).

Partial use cases may require a plurality of categories for optimizationand other use cases may focus only upon one key performance indicator(KPI). 5G supports such various use cases using a flexible and reliablemethod.

eMBB far surpasses basic mobile Internet access and covers abundantbidirectional work and media and entertainment applications in cloud andaugmented reality. Data is one of 5G core motive forces and, in a 5Gera, a dedicated voice service may not be provided for the first time.In 5G, it is expected that voice will be simply processed as anapplication program using data connection provided by a communicationsystem. Main causes for increased traffic volume are due to an increasein the size of content and an increase in the number of applicationsrequiring high data transmission rate. A streaming service (of audio andvideo), conversational video, and mobile Internet access will be morewidely used as more devices are connected to the Internet. These manyapplication programs require connectivity of an always turned-on statein order to push real-time information and alarm for users. Cloudstorage and applications are rapidly increasing in a mobilecommunication platform and may be applied to both work andentertainment. The cloud storage is a special use case which acceleratesgrowth of uplink data transmission rate. 5G is also used for remote workof cloud. When a tactile interface is used, 5G demands much lowerend-to-end latency to maintain user good experience. Entertainment, forexample, cloud gaming and video streaming, is another core element whichincreases demand for mobile broadband capability. Entertainment isessential for a smartphone and a tablet in any place including highmobility environments such as a train, a vehicle, and an airplane. Otheruse cases are augmented reality for entertainment and informationsearch. In this case, the augmented reality requires very low latencyand instantaneous data volume.

In addition, one of the most expected 5G use cases relates a functioncapable of smoothly connecting embedded sensors in all fields, i.e.,mMTC. It is expected that the number of potential IoT devices will reach204 hundred million up to the year of 2020. An industrial IoT is one ofcategories of performing a main role enabling a smart city, assettracking, smart utility, agriculture, and security infrastructurethrough 5G.

URLLC includes a new service that will change industry through remotecontrol of main infrastructure and an ultra-reliable/availablelow-latency link such as a self-driving vehicle. A level of reliabilityand latency is essential to control a smart grid, automatize industry,achieve robotics, and control and adjust a drone.

5G is a means of providing streaming evaluated as a few hundred megabitsper second to gigabits per second and may complement fiber-to-the-home(FTTH) and cable-based broadband (or DOCSIS). Such fast speed is neededto deliver TV in resolution of 4 K or more (6 K, 8 K, and more), as wellas virtual reality and augmented reality. Virtual reality (VR) andaugmented reality (AR) applications include almost immersive sportsgames. A specific application program may require a special networkconfiguration. For example, for VR games, gaming companies need toincorporate a core server into an edge network server of a networkoperator in order to minimize latency.

Automotive is expected to be a new important motivated force in 5Gtogether with many use cases for mobile communication for vehicles. Forexample, entertainment for passengers requires high simultaneouscapacity and mobile broadband with high mobility. This is because futureusers continue to expect connection of high quality regardless of theirlocations and speeds. Another use case of an automotive field is an ARdashboard. The AR dashboard causes a driver to identify an object in thedark in addition to an object seen from a front window and displays adistance from the object and a movement of the object by overlappinginformation talking to the driver. In the future, a wireless moduleenables communication between vehicles, information exchange between avehicle and supporting infrastructure, and information exchange betweena vehicle and other connected devices (e.g., devices accompanied by apedestrian). A safety system guides alternative courses of a behavior sothat a driver may drive more safely drive, thereby lowering the dangerof an accident. The next stage will be a remotely controlled orself-driven vehicle. This requires very high reliability and very fastcommunication between different self-driven vehicles and between avehicle and infrastructure. In the future, a self-driven vehicle willperform all driving activities and a driver will focus only uponabnormal traffic that the vehicle cannot identify. Technicalrequirements of a self-driven vehicle demand ultra-low latency andultra-high reliability so that traffic safety is increased to a levelthat cannot be achieved by human being.

A smart city and a smart home/building mentioned as a smart society willbe embedded in a high-density wireless sensor network. A distributednetwork of an intelligent sensor will identify conditions for costs andenergy-efficient maintenance of a city or a home. Similar configurationsmay be performed for respective households. All of temperature sensors,window and heating controllers, burglar alarms, and home appliances arewirelessly connected. Many of these sensors are typically low in datatransmission rate, power, and cost. However, real-time HD video may bedemanded by a specific type of device to perform monitoring.

Consumption and distribution of energy including heat or gas isdistributed at a higher level so that automated control of thedistribution sensor network is demanded. The smart grid collectsinformation and connects the sensors to each other using digitalinformation and communication technology so as to act according to thecollected information. Since this information may include behaviors of asupply company and a consumer, the smart grid may improve distributionof fuels such as electricity by a method having efficiency, reliability,economic feasibility, production sustainability, and automation. Thesmart grid may also be regarded as another sensor network having lowlatency.

Mission critical application (e.g. e-health) is one of 5G use scenarios.A health part contains many application programs capable of enjoyingbenefit of mobile communication. A communication system may supportremote treatment that provides clinical treatment in a faraway place.Remote treatment may aid in reducing a barrier against distance andimprove access to medical services that cannot be continuously availablein a faraway rural area. Remote treatment is also used to performimportant treatment and save lives in an emergency situation. Thewireless sensor network based on mobile communication may provide remotemonitoring and sensors for parameters such as heart rate and bloodpressure.

Wireless and mobile communication gradually becomes important in thefield of an industrial application. Wiring is high in installation andmaintenance cost. Therefore, a possibility of replacing a cable withreconstructible wireless links is an attractive opportunity in manyindustrial fields. However, in order to achieve this replacement, it isnecessary for wireless connection to be established with latency,reliability, and capacity similar to those of the cable and managementof wireless connection needs to be simplified. Low latency and a verylow error probability are new requirements when connection to 5G isneeded.

Logistics and freight tracking are important use cases for mobilecommunication that enables inventory and package tracking anywhere usinga location-based information system. The use cases of logistics andfreight typically demand low data rate but require location informationwith a wide range and reliability.

FIG. 7 illustrates a data flow example at a transmitting device in theNR system.

In FIG. 7 , an RB denotes a radio bearer. Referring to FIG. 7 , atransport block is generated by MAC by concatenating two RLC PDUs fromRBx and one RLC PDU from RBy. In FIG. 7 , the two RLC PDUs from RBx eachcorresponds to one IP packet (n and n+1) while the RLC PDU from RBy is asegment of an IP packet (m). In NR, a RLC SDU segment can be located inthe beginning part of a MAC PDU and/or in the ending part of the MACPDU. The MAC PDU is transmitted/received using radio resources through aphysical layer to/from an external device.

FIG. 8 illustrates an example of a slot structure available in a newradio access technology (NR).

To reduce or minimize data transmission latency, in a 5G new RAT, a slotstructure in which a control channel and a data channel aretime-division-multiplexed is considered.

In the example of FIG. 8 , the hatched area represents the transmissionregion of a DL control channel (e.g., PDCCH) carrying the DCI, and theblack area represents the transmission region of a UL control channel(e.g., PUCCH) carrying the UCI. Here, the DCI is control informationthat the gNB transmits to the UE. The DCI may include information oncell configuration that the UE should know, DL specific information suchas DL scheduling, and UL specific information such as UL grant. The UCIis control information that the UE transmits to the gNB. The UCI mayinclude a HARQ ACK/NACK report on the DL data, a CSI report on the DLchannel status, and a scheduling request (SR).

In the example of FIG. 8 , the region of symbols from symbol index 1 tosymbol index 12 may be used for transmission of a physical channel(e.g., a PDSCH) carrying downlink data, or may be used for transmissionof a physical channel (e.g., PUSCH) carrying uplink data. According tothe slot structure of FIG. 8 , DL transmission and UL transmission maybe sequentially performed in one slot, and thus transmission/receptionof DL data and reception/transmission of UL ACK/NACK for the DL data maybe performed in one slot. As a result, the time taken to retransmit datawhen a data transmission error occurs may be reduced, thereby minimizingthe latency of final data transmission.

In such a slot structure, a time gap is needed for the process ofswitching from the transmission mode to the reception mode or from thereception mode to the transmission mode of the gNB and UE. On behalf ofthe process of switching between the transmission mode and the receptionmode, some OFDM symbols at the time of switching from DL to UL in theslot structure are set as a guard period (GP).

In the legacy LTE/LTE-A system, a DL control channel istime-division-multiplexed with a data channel and a PDCCH, which is acontrol channel, is transmitted throughout an entire system band.However, in the new RAT, it is expected that a bandwidth of one systemreaches approximately a minimum of 100 MHz and it is difficult todistribute the control channel throughout the entire band fortransmission of the control channel. For data transmission/reception ofa UE, if the entire band is monitored to receive the DL control channel,this may cause increase in battery consumption of the UE anddeterioration in efficiency. Accordingly, in the present disclosure, theDL control channel may be locally transmitted or distributivelytransmitted in a partial frequency band in a system band, i.e., achannel band.

In the NR system, the basic transmission unit is a slot. A duration ofthe slot includes 14 symbols having a normal cyclic prefix (CP) or 12symbols having an extended CP. In addition, the slot is scaled in timeas a function of a used subcarrier spacing.

Hereinafter, when a PDCP Data PDU is received from lower layers, actionsof the receiving PDCP entity are explained. For convenience ofexplanation, definitions of parameter used in the actions are defined inadvance.

-   -   HFN(State Variable): the HFN part (i.e. the number of most        significant bits equal to HFN length) of the State Variable;    -   SN(State Variable): the SN part (i.e. the number of least        significant bits equal to PDCP SN length) of the State Variable;    -   RCVD_SN: the PDCP SN of the received PDCP Data PDU, included in        the PDU header;    -   RCVD_HFN: the HFN of the received PDCP Data PDU, calculated by        the receiving PDCP entity;    -   RCVD_COUNT: the COUNT of the received PDCP Data PDU=[RCVD_HFN,        RCVD_SN].

At reception of a PDCP Data PDU from lower layers, the receiving PDCPentity shall determine the COUNT value of the received PDCP Data PDU,i.e. RCVD_COUNT, as follows:

-   -   if RCVD_SN<SN(RX_DELIV)−Window_Size, RCVD_HFN sets to        HFN(RX_DELIV)+1.    -   else if RCVD_SN>=SN(RX_DELIV)+Window_Size . . . RCVD_HFN sets to        HFN(RX_DELIV)−1.    -   else, RCVD_HFN should set to HFN(RX_DELIV).

Finally, RCVD_COUNT is determined to [RCVD_HFN, RCVD_SN].

After determining the COUNT value of the received PDCP Data PDU, thereceiving PDCP entity shall perform deciphering and integrityverification of the PDCP Data PDU using COUNT=RCVD_COUNT. When theintegrity verification fails, the receiving PDCP entity shall indicatethe integrity verification failure to upper layer and discard the PDCPData PDU. If RCVD_COUNT<RX_DELIV or if the PDCP Data PDU withCOUNT=RCVD_COUNT has been received before, the receiving PDCP entityshall discard the PDCP Data PDU.

If the received PDCP Data PDU with COUNT valu =RCVD_COUNT is notdiscarded above, the receiving PDCP entity shall store the resultingPDCP SDU in the reception buffer.

In this case, if RCVD_COUNT>=RX_NEXT, the receiving PDCP entity shallupdate RX_NEXT to RCVD_COUNT+1. Further, if outOfOrderDelivery isconfigured, the receiving PDCP entity shall deliver the resulting PDCPSDU to upper layers.

While, if RCVD_COUNT=RX_DELIV, the receiving PDCP entity shall deliverall stored PDCP SDU(s) with consecutively associated COUNT value(s) isstarted from COUNT=RX_DELIV to upper layers in ascending order of theassociated COUNT value after performing header decompression when notdecompressed before and update RX_DELIV to the COUNT value of the firstPDCP SDU which has not been delivered to upper layers, with COUNTvalue>RX_DELIV.

Furthermore, if t-Reordering is running, and if RX_DELIV>=RX_REORD, thereceiving PDCP entity shall stop and reset t-Reordering. If t-Reorderingis not running (includes the case when t-Reordering is stopped due toactions above), and RX_DELIV<RX_NEXT, the receiving PDCP entity shallupdate RX_REORD to RX_NEXT and start t-Reordering.

When t-Reordering expires, the receiving PDCP entity shall deliver allstored PDCP SDU(s) with associated COUNT value(s) <RX_REORD or allstored PDCP SDU(s) with consecutively associated COUNT value(s) startingfrom RX_REORD to upper layers in ascending order of the associated COUNTvalue after performing header decompression when not decompressedbefore. Further, the receiving PDCP entity should update RX_DELIV to theCOUNT value of the first PDCP SDU which has not been delivered to upperlayers, with COUNT value>=RX_REORD.

If RX_DELIV<RX_NEXT, the receiving PDCP entity should update RX_REORD toRX_NEXT and start t-Reordering.

When the value of the t-Reordering is reconfigured by upper layers whilethe t-Reordering is running, the UE shall update RX_REORD to RX_NEXT.Further, the UE shall stop and restart t-Reordering.

RX_NEXT indicates the COUNT value of the next PDCP SDU expected to bereceived. The initial value is 0.

RX_DELIV indicates the COUNT value of the first PDCP SDU not deliveredto the upper layers, but still waited for. The initial value is 0.

RX_REORD indicates the COUNT value following the COUNT value associatedwith the PDCP Data PDU which triggered t-Reordering.

RX_NEXT, RX DELIV and RX_REORD are the state variable.

Above three state variables are non-negative integers, and take valuesfrom 0 to [2³²−1].

Window_Size indicates the constant size of the reordering window. Thevalue equals to 2^([pdcp−SN−Size])−1.

Hereinafter, Integrity protection and verification are explained.

The integrity protection function includes both integrity protection andintegrity verification and is performed in PDCP, if configured. The dataunit that is integrity protected is the PDU header and the data part ofthe PDU before ciphering. The integrity protection is always applied toPDCP Data PDUs of SRBs. The integrity protection is applied to PDCP DataPDUs of DRBs for which integrity protection is configured. The integrityprotection is not applicable to PDCP Control PDUs.

The integrity protection algorithm and key to be used by the PDCP entityare configured by upper layers. The integrity protection function isactivated by upper layers. When security is activated, the integrityprotection function shall be applied to all PDUs including andsubsequent to the PDU indicated by upper layers for the downlink and theuplink, respectively.

For downlink and uplink integrity protection and verification, theparameters required by PDCP for integrity protection are input to theintegrity protection algorithm. The required inputs to the integrityprotection function include the COUNT value, and DIRECTION (direction ofthe transmission). The parameters required by PDCP which are provided byupper layers are:

-   -   BEARER (defined as the radio bearer identifier. It will use the        value RB identity−1);    -   KEY (the integrity protection keys for the control plane and for        the user plane are KRRCint and KUPint, respectively).

At transmission, the UE computes the value of the MAC-I field and atreception it verifies the integrity of the PDCP Data PDU by calculatingthe X-MAC based on the input parameters as specified above. If thecalculated X-MAC corresponds to the received MAC-I, integrity protectionis verified successfully.

In the NR system, even if the integrity verification for the data radiobearers (DRBs) fails, the UE does not perform a RRC ConnectionRe-establishment procedure. When the integrity verification for a PDCPData PDU for DRB fails, the PDCP entity indicates the integrityverification failure and discards the PDCP Data PDU.

However, there is a case where a PDCP Data PDU is discarded even if thePDCP Data PDU can be delivered to the upper layer due to the integrityverification operation. For example, when a receiving PDCP entityreceives a PDCP Data PDU, the receiving PDCP entity performs theintegrity verification to the PDCP Data PDU. If the integrityverification fails, the receiving PDCP entity discards the PDCP DataPDU. After that, when the receiving PDCP entity receives a PDCP Data PDUwhich has the same COUNT value as the PDCP Data PDU that has failedintegrity verification, the receiving PDCP entity discards the PDCP DataPDU regardless of whether the integrity verification of the PDCP DataPDU succeeds.

If this case happens, an user experience would be worsened. For example,the throughput may be decreased. Thus, a new procedure is required tohandle the above case.

FIG. 9 shows a flow chart of the present invention.

Referring to FIG. 9 , in S101, a receiving device (e.g., a receivingPDCP entity in the receiving device) receives a PDCP Data PDU which hasthe same COUNT value of a previously received PDCP Data PDU. And, inS102, the receiving device determines whether the integrity verificationwas successful for the previously received PDCP Data PDU or not.

If the integrity verification was failed for the previously receivedPDCP Data PDU, the receiving device considers that the PDCP Data PDUwith the COUNT value has not been received before, and may perform theintegrity verification for the PDCP Data PDU with the same COUNT valueas that of the previously received PDCP Data PDU, in S103. The receivingdevice stores the received PDCP Data PDU in the reception buffer if theCOUNT value of the PDCP Data PDU is within the reception window and theintegrity verification of the PDCP Data PDU is successful.

However, if the integrity verification was successful for the previouslyreceived PDCP Data PDU, the receiving device performs the integrityverification and discards the received PDCP Data PDU in S104.

As mentioned above, after determining the COUNT value of the receivedPDCP Data PDU, the receiving PDCP entity shall perform deciphering andintegrity verification of the PDCP Data PDU using COUNT=RCVD_COUNT. Whenthe integrity verification fails, the receiving PDCP entity shallindicate the integrity verification failure to upper layer and discardthe PDCP Data PDU.

According to the present invention, if RCVD_COUNT<RX_DELIV or if thePDCP Data PDU with COUNT=RCVD_COUNT has been received and integrityverification was successful before, the receiving PDCP entity shalldiscard the PDCP Data PDU. That us, a condition related to whether theintegrity verification was successful before or not should be added.

Alternatively, if RCVD_COUNT<RX_DELIV or if the PDCP Data PDU withCOUNT=RCVD_COUNT has been stored in the reception buffer before, thereceiving PDCP entity shall discard the PDCP Data PDU

This invention can be applicable to SRBs, AM DRBs, UM DRBs, and TM DRBs.The upper layer can be RRC, NAS, and SDAP. The lower layer can be RLCand MAC.

FIG. 10 shows an example according to an embodiment of the presentinvention. In FIG. 10 , it is assumed that a receiving device (e.g., thereceiving PDCP entity of the receiving device) is configured withintegrity function. For example, a receiving PDCP entity at a receivingdevice may be configured with integrity function.

In T=0: at reception of a PDCP Data PDU (from lower layer), thereceiving device shall determine the COUNT value of the received PDCPData PDU (i.e., the COUNT value=100), and perform the deciphering andintegrity verification. Since, the integrity verification in T=0 fails,the receiving device shall discard the PDCP Data PDU.

In T=1: at reception of a PDCP Data PDU (from lower layer), thereceiving device shall determine the COUNT value of the received PDCPData PDU (i.e., the COUNT value=100), and perform the deciphering andintegrity verification. Since, the integrity verification in T=1successes, the receiving device shall store the PDCP SDU in thereception buffer and deliver the PDCP Data PDU to upper layer.

In T=2: at reception of a PDCP Data PDU (via lower layer from atransmitting device), the receiving device shall determine the COUNTvalue of the received PDCP Data PDU (i.e., the COUNT value=101), andperform the deciphering and integrity verification. Since, the integrityverification in T=2 successes, the receiving device shall store the PDCPSDU in the reception buffer and deliver the PDCP Data PDU to upperlayer.

In T=3: at reception of a PDCP Data PDU (via lower layer from atransmitting device), the receiving device shall determine the COUNTvalue of the received PDCP Data PDU (i.e., the COUNT value=101), andperform the deciphering and integrity verification. Since, the integrityverification in T=3 fails, the receiving device shall Indicate theintegrity verification failure (to upper layer/entity above thereceiving PDCP entity) and discard the PDCP Data PDU.

In T=4: at reception of a PDCP Data PDU (via lower layer from atransmitting device), the receiving device shall determine the COUNTvalue of the received PDCP Data PDU (i.e., the COUNT value=102), andperform the deciphering and integrity verification. Since, the integrityverification in T=4 fails, the receiving device shall Indicate theintegrity verification failure (to upper layer/entity above thereceiving PDCP entity) and discard the PDCP Data PDU.

In T=5: at reception of a PDCP Data PDU (via lower layer from atransmitting device), the receiving device shall determine the COUNTvalue of the received PDCP Data PDU (i.e., the COUNT value=102), andperform the deciphering and integrity verification. Since, the integrityverification in T=5 fails, the receiving device shall Indicate theintegrity verification failure (to upper layer/entity above thereceiving PDCP entity) and discard the PDCP Data PDU.

While, in T=6: at reception of a PDCP Data PDU (via lower layer from atransmitting device), the receiving device shall determine the COUNTvalue of the received PDCP Data PDU (i.e., the COUNT value=103), andperform the deciphering and integrity verification. Since, the integrityverification in T=6 successes, the receiving device shall store the PDCPSDU in the reception buffer and start t-Reordering.

In T=7: at reception of a PDCP Data PDU (via lower layer from atransmitting device), the receiving device shall determine the COUNTvalue of the received PDCP Data PDU (i.e., the COUNT value=103), andperform the deciphering and integrity verification. Since, the integrityverification in T=6 successes, the receiving device shall Discard thePDCP Data PDU.

Finally, in T=8: when t-Reordering expire, the receiving device deliverthe PDCP Data PDU associated with COUNT value=103 (to upper layer/entityabove the receiving PDCP entity).

FIG. 11 is a block diagram illustrating an example of elements of atransmitting device 100 and a receiving device 200 according to someimplementations of the present disclosure.

The transmitting device 100 and the receiving device 200 respectivelyinclude transceivers 13 and 23 capable of transmitting and receivingradio signals carrying information, data, signals, and/or messages,memories 12 and 22 for storing information related to communication in awireless communication system, and processors 11 and 21 operationallyconnected to elements such as the transceivers 13 and 23 and thememories 12 and 22 to control the elements and configured to control thememories 12 and 22 and/or the transceivers 13 and 23 so that acorresponding device may perform at least one of the above-describedimplementations of the present disclosure.

The memories 12 and 22 may store programs for processing and controllingthe processors 11 and 21 and may temporarily store input/outputinformation. The memories 12 and 22 may be used as buffers. The buffersat each protocol layer (e.g. PDCP, RLC, MAC) are parts of the memories12 and 22.

The processors 11 and 21 generally control the overall operation ofvarious modules in the transmitting device and the receiving device.Especially, the processors 11 and 21 may perform various controlfunctions to implement the present disclosure. For example, theoperations occurring at the protocol stacks (e.g. PDCP, RLC, MAC and PHYlayers) according to the present disclosure may be performed by theprocessors 11 and 21. The protocol stacks performing operations of thepresent disclosure may be parts of the processors 11 and 21.

The processors 11 and 21 may be referred to as controllers,microcontrollers, micro-processors, or microcomputers. The processors 11and 21 may be implemented by hardware, firmware, software, or acombination thereof. In a hardware configuration, application specificintegrated circuits (ASICs), digital signal processors (DSPs), digitalsignal processing devices (DSPDs), programmable logic devices (PLDs), orfield programmable gate arrays (FPGAs) may be included in the processors11 and 21. The present disclosure may be implemented using firmware orsoftware, and the firmware or software may be configured to includemodules, procedures, functions, etc. performing the functions oroperations of the present disclosure. Firmware or software configured toperform the present disclosure may be included in the processors 11 and21 or stored in the memories 12 and 22 so as to be driven by theprocessors 11 and 21.

The processor 11 of the transmitting device 100 performs predeterminedcoding and modulation for a signal and/or data scheduled to betransmitted to the outside by the processor 11 or a scheduler connectedwith the processor 11, and then transfers the coded and modulated datato the transceiver 13. For example, the processor 11 converts a datastream to be transmitted into K layers through demultiplexing, channelcoding, scrambling, and modulation. The coded data stream is alsoreferred to as a codeword and is equivalent to a transport block whichis a data block provided by a MAC layer. One transport block (TB) iscoded into one codeword and each codeword is transmitted to thereceiving device in the form of one or more layers. For frequencyup-conversion, the transceiver 13 may include an oscillator. Thetransceiver 13 may include Nt (where Nt is a positive integer)transmission antennas.

A signal processing process of the receiving device 200 is the reverseof the signal processing process of the transmitting device 100. Undercontrol of the processor 21, the transceiver 23 of the receiving device200 receives radio signals transmitted by the transmitting device 100.The transceiver 23 may include Nr (where Nr is a positive integer)receive antennas and frequency down-converts each signal receivedthrough receive antennas into a baseband signal. The processor 21decodes and demodulates the radio signals received through the receptionantennas and restores data that the transmitting device 100 intended totransmit.

The transceivers 13 and 23 include one or more antennas. An antennaperforms a function for transmitting signals processed by thetransceivers 13 and 23 to the exterior or receiving radio signals fromthe exterior to transfer the radio signals to the transceivers 13 and23. The antenna may also be called an antenna port. Each antenna maycorrespond to one physical antenna or may be configured by a combinationof more than one physical antenna element. The signal transmitted fromeach antenna cannot be further deconstructed by the receiving device200. An RS transmitted through a corresponding antenna defines anantenna from the view point of the receiving device 200 and enables thereceiving device 200 to derive channel estimation for the antenna,irrespective of whether the channel represents a single radio channelfrom one physical antenna or a composite channel from a plurality ofphysical antenna elements including the antenna. That is, an antenna isdefined such that a channel carrying a symbol of the antenna can beobtained from a channel carrying another symbol of the same antenna. Antransceiver supporting a MIMO function of transmitting and receivingdata using a plurality of antennas may be connected to two or moreantennas. The transceivers 13 and 23 may be referred to as radiofrequency (RF) units.

In the implementations of the present disclosure, a UE operates as thetransmitting device 100 in UL and as the receiving device 200 in DL. Inthe implementations of the present disclosure, a BS operates as thereceiving device 200 in UL and as the transmitting device 100 in DL.Hereinafter, a processor, a transceiver, and a memory included in the UEwill be referred to as a UE processor, a UE transceiver, and a UEmemory, respectively, and a processor, a transceiver, and a memoryincluded in the BS will be referred to as a BS processor, a BStransceiver, and a BS memory, respectively.

The UE processor can be configured to operate according to the presentdisclosure, or control the UE transceiver to receive or transmit signalsaccording to the present disclosure. The BS processor can be configuredto operate according to the present disclosure, or control the BStransceiver to receive or transmit signals according to the presentdisclosure.

The processor 11 (at a UE and/or at a BS) checks whether there is a ULgrant or DL assignment for a serving cell in a time unit. If there is aUL grant or DL assignment for the serving cell in the time unit, theprocessor 11 checks whether a data unit is actually present on the ULgrant or DL assignment in the time unit, in order to determine whetherto restart a deactivation timer associated with the serving cell whichhas been started. The processor 11 restarts the deactivation timerassociated with the serving cell in the time unit if there is a dataunit present on the UL grant or DL assignment in the time unit. Theprocessor 11 does not restart the deactivation timer associated with theserving cell in the time unit if there is no data unit present on the ULgrant or DL assignment in the time unit, unless another condition thatthe processor 11 should restart the deactivation timer is satisfied. Theprocessor 11 does not restart the deactivation timer associated with theserving cell in the time unit if there is no data unit present on the ULgrant or DL assignment in the time unit and if an activation command foractivating the serving cell is not present in the time unit. Theprocessor 11 may be configured to check whether a data unit is actuallypresent on the UL grant or DL assignment on the serving cell in the timeunit in order to determine whether to restart the deactivation timer ofthe serving cell, if the UL grant or DL assignment is a configuredgrant/assignment which is configured by RRC to occur periodically on theserving cell. The processor 11 may be configured to check whether a dataunit is actually present on the UL grant or DL assignment on the servingcell in the time unit in order to determine whether to restart thedeactivation timer of the serving cell, if the UL grant or the DLassignment is a dynamic grant/assignment which is indicated by a PDCCH.The processor 11 may be configured to check whether a data unit isactually present on the UL grant or DL assignment on the serving cell inthe time unit in order to determine whether to restart the deactivationtimer of the serving cell, if the serving cell is a SCell of the UE. Theprocessor 11 (at the UE and/or the BS) deactivates the serving cell uponexpiry of the deactivation timer associated with the serving cell.

According to the present invention, when a transceiver 23 at a receivingdevice 200 may receive signals containing PDCP PDUs. When the processor21 (e.g., at a PDCP entity configured in the processor 21) receives aPDCP Data PDU which has the same COUNT value of a previously receivedPDCP Data PDU, the processor 21 performs the integrity verification andmay discard the currently received PDCP Data PDU if the integrityverification was successful for the previously received PDCP Data PDU.Else, if the integrity verification was failed for the previouslyreceived PDCP Data PDU, the processor 21 considers that the PDCP DataPDU with the COUNT value has not been received before. If the integrityverification was failed for the previously received PDCP Data PDU, theprocessor 21 may be configured to perform the integrity verification forthe currently PDCP Data PDU with the same COUNT value. The processor 21stores the currently received PDCP Data PDU in the reception buffer(e.g., in the memory 22) if the COUNT value of the currently receivedPDCP Data PDU is within the reception window and the integrityverification of the currently received PDCP Data PDU is successful.

As described above, the detailed description of the preferredimplementations of the present disclosure has been given to enable thoseskilled in the art to implement and practice the disclosure. Althoughthe disclosure has been described with reference to exemplaryimplementations, those skilled in the art will appreciate that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the disclosure describedin the appended claims. Accordingly, the disclosure should not belimited to the specific implementations described herein, but should beaccorded the broadest scope consistent with the principles and novelfeatures disclosed herein.

INDUSTRIAL APPLICABILITY

The implementations of the present disclosure are applicable to anetwork node (e.g., BS), a UE, or other devices in a wirelesscommunication system.

The invention claimed is:
 1. A method for processing data units by aPacket Data Convergence Protocol (PDCP) entity of a user equipment (UE)in a wireless communication system, the method comprising: receiving afirst PDCP protocol data unit (PDU) having a COUNT value from a lowerlayer; performing an integrity verification for the first PDCP PDU basedon the COUNT value; based on the integrity verification for the firstPDCP PDU failing, discarding the first PDCP PDU and considering thefirst PDCP PDU as not received; based on at least one PDCP PDU havingthe COUNT value being received before, discarding the first PDCP PDU;and based on the first PDCP PDU being not discarded, storing a PDCPservice data unit (SDU) of the first PDCP PDU in a reception buffer. 2.The method of claim 1, further comprising: receiving a second PDCP PDUhaving the COUNT value from the lower layer, wherein, based on theintegrity verification for the first PDCP PDU having failed and based onthe integrity verification for the second PDCP PDU succeeding, the firstPDCP PDU is considered as not received, and wherein the second PDCP PDUis stored in the reception buffer.
 3. The method of claim 2, wherein thesecond PDCP PDU is a duplicated PDCP PDU of the first PDCP PDU.
 4. Themethod of claim 1, further comprising: based on the integrityverification for the first PDCP PDU failing, transmitting an indicationrelated to a failure of the integrity verification for the first PDCPPDU to an upper layer.
 5. A user equipment (UE) in a wirelesscommunication system, the UE comprising: at least one transceiver; atleast one processor; and at least one computer memory operablyconnectable to the at least one processor and storing instructions that,when executed, cause the at least one processor to perform operations ina Packet Data Convergence Protocol (PDCP) entity of UE comprising:receiving a first PDCP protocol data unit (PDU) having a COUNT valuefrom a lower layer; performing an integrity verification for the firstPDCP PDU based on the COUNT value; based on the integrity verificationfor the first PDCP PDU failing, discarding the first PDCP PDU andconsidering the first PDCP PDU as not received; based on at least onePDCP PDU having the COUNT value being received before, discarding thefirst PDCP PDU; and based on the first PDCP PDU being not discarded,storing a PDCP service data unit (SDU) of the first PDCP PDU in areception buffer.
 6. The UE of claim 5, wherein the operations furthercomprise: receiving a second PDCP PDU having the COUNT value from thelower layer, wherein, based on the integrity verification for the firstPDCP PDU having failed and based on the integrity verification for thesecond PDCP PDU succeeding, the first PDCP PDU is considered as notreceived, and wherein the second PDCP PDU is stored in the receptionbuffer.
 7. The UE of claim 5, wherein the operations further comprise:based on the integrity verification for the first PDCP PDU failing,transmitting an indication related to a failure of the integrityverification for the first PDCP PDU to an upper layer.
 8. The UE ofclaim 6, wherein the second PDCP PDU is a duplicated PDCP PDU of thefirst PDCP PDU.